Circuit interrupter and method of making the same



April 24, 1956 R. c. DicKlNsoN ETAL 2,743,336

CIRCUIT INTERRUPTER AND METHOD OF MAKING THE SAME Filed Nov. 28, 1952 2Sheets-Sheet l 22 11 2|- SQ' CS) l f1 'l Il I l L' I s l I "4 I Il y lIl :l Il L ls |g a l l l l (M d l lI *10S L9 I' /5 'I s wlTNEssEs;INVENTORS Russell E.Frink d M 8 and Reben c oickinson.

April 24, 1956 R. c. DICKINSON ErAL 2,743,336

CIRCUIT INTERRUPTER AND METHOD OF' MAKING THE SAME United States PatentO vCIRCUIT INTERRUIYIER AND Mnmon or MAKING THE SAME Robert C. Dickinsonand Russell E. Frink, Pittsburgh, Pa., assignors to WestinghouseElectric Corporation, East Pittsburgh, Pa., a corporation ofPennsylvania Application November 2s, 1952, serial No. 323,010 s claims.(c1. zou- 144) side-wall members cooperating to provide an improved arcchute of the spaced slotted plate type.

A further object of our invention is to provide an improved process ormethod of manufacturing arc-chute side-wall members of the foregoingtype.

Further objects and advantages willl readily become apparent uponreading the following specification, taken in conjunction with thedrawings, in which Figure 1 is a side elevational view, partially invertical section, showing a circuit interrupter embodying our invention,the contact structure being shown in thel closedcircuit position;

Fig. 2 is a fragmentary, vertical sectional view taken along the lineII-II of Fig. 1;

' Fig. 3 is a sectional view through one of our finished, insulating,side-wall members; n

Fig. 4 is a fragmentary top plan view of the finished insulating,sideawall member of Fig. 3;

Fig. 5 is a fragmentary view looking at thel other, or lower, end of theside-wall member of Fig. 3;

` Fig. 6 is a fragmentary, sectional view taken substantially along theline VI-VI of Fig. 2;

Fig. 7 is a fragmentary, lower-end view of the insulat ing blank used informing one of our finished, insulating side-wall members; and

Fig. 8 is a fragmentary view, partially in section, showing the cuttingoperation being performed upon a blank such as shown in Fig. 7.

Referring to the drawings, and more particularly to Fig. 1 thereof, thereference numeral 1 generally designates suitable contact structurewhich, when separated to the open-circuit position, establishes lan arcwhich is moved upwardly into an arc chute, generally designated by thereference numeral 2 as a result of the transverse magnetic eld set up bythe blowout coil 3 and associated magnet structure 4. A rotatablecontact arm 5 carries a conducting bridge 6, which, in theclosed-circuit position, as shown in Fig. 1, interconnects stationarymain contacts 7, 8

A contact stud 9 carries the current from the stationary main contact 7,through an insulating bushing 10 to the external circuit. The contactstud for the stationary mainy contact 8 is not shown, but it may beidentical to the contact stud 9. l

Consequently, in the closed-circuit position of the interrupter, asshown in Fig. 1, the electrical circuit comprises the contact stud 9,stationary main contact 7, conducting bridge 6, stationary main contact8, to the Contact stud therefor, not shown, to the external circuit.

-During the opening operation of the interrupter, the contact arm 5 isrotated in a clockwise direction about. a pivot pin, not shown, butwhich is in electrical contact with the stationary main contact 8, todraw an arc between the arcing contacts 11, 12 after the separation ofconducting bridge 6 from the main contacts 7, 8.

When the arcing contacts 11, 12 separate, the arc formed therebetweenwill expand upwardly because of the loop circuit so that one terminalthereof will be transferred to the arc terminal member 18, and the otherarc terminal will be transferred to the other arc terminal member 19.

When this occurs, the blowout coil 3 will be put into series circuit,and the transverse magnetic field set up thereby between the field polemembers 14 (Fig. 2) will move the established arc upwardly along the arcterminal members 18, 19 into the arc chute 2. The electrical circuit nowcomprises contact stud 9, conductor 20, blow out coil 3, contact clip15, arc terminal member 18, the arc itself, arc terminal member 19,exible shunt 28, contact arm 5 to the other contact stud, not shown.

The arc chute 2 comprises an insulating rectangularlyf shaped housingmember 22 positioned adjacent to an insulating plate 21, the latterserving as a base for the blowout coil 3. Within the housing 22 isplaced a parot' mating or cooperating identical insulating spacedsidewall members 23, 24. Fig. 3 shows a sectional` view through one ofthe insulating side-wall members 24. It will be noted that the side-wallmember 24 has a v side-wall portion 24a, and a plurality of primaryridges 24h. Preferably, each primary ridge 24b has an offset portion24e, the purpose for which will be more apparent hereinafter. Disposedbetween adjacent primary ridges 24b are a plurality of secondary ridges24d, the configuration of which is more clearly apparent from aninspection of Figs. 4 and 5 of the drawings.

Thus, upon assembling the two side-wa1l members 23, 24, the offsetportions 24C of the side-wall member 24 engage the side-wall portion 23aof the side-wall member 23. Also, the secondary ridges 24d of theside-,wall member 24 cooperate with the primary ridges 231)4 of theside-wall member 23, in a manner more clearly shown in Fig. 2 of thedrawings.

It will be noted that the primary ridges of one side-wall member are insubstantially the same plane as the sec ondary ridges of the otherside-wall member, so that the effect of assembling two of the side-wallmembers 23, 24 results essentially in a spaced-slotted-plateconstruction, as more clearly shown in Figs. 2 and 6 of the drawings.

We are well aware of .prior-art constructions involving such aninterleaving ridge arrangement, such as shown in U. S. Patent 2,417,683,issued March 18, 1947, to Winton G. Harlow. Such a prior-art arc chutehas the primary ridges themselves engaging the opposite side-wallmember, so that the arc is compelled to contact the opposite side-wallmember. However, in our construction, as shown in Fig. 6, the arc,indicated by the dotted line 25, never reaches the side-wall portions23a, 24a,'but is cooled and deionized by the cool surfaces and the coolfluid contained within the notches 26, provided between primary andsecondary ridges extending from the same wall member. These notches orpockets 26 provide cool surfaces and a quantity of un-ionized gas whichcools the arc 2S and brings about its rapid extinction. Moreover, ourimproved construction, unlike the prior-art arrangements, does notpermit the arc to move along the outer edge of the primary ridges nearthe exhaust end of the arc chute. As indicated in Figs, 2 and 3, the arc25 moves up to the point A, where it is stopped by the solid insulatingmaterial forming the offset ridge portion 23C or 24C. Hence, the arc 25is effectively trapped at this point A, and has no tendency to wear itsway along to the exhaust end of the arc chute 2.

. AI"`ig..7 indicates how a blank side-wall member is con,.-

' these jplates are arenoso figured. 'As shown, there are provided deepand shallow valleys 51, -32 -intheblanking'operation Thus, Fig. 7"

shows a fragmentary lower-end view of a blank, in which the shallowvalley 32 is bounded or defined by the sides of the uniinishe'dridges 33and by the 'tops kof theuniinishe'd secondaryridges. As'shown in Fig."8,`by employing a gang of `spaced 'cutters l56, separatedby spacers 37,37a and arranged for 'simultaneous `actuation on the 'same cuttershaft'38, the blank of Fig. 7 may b'erunthrough against the cutter gang;to' result in the cutters r36, nishiug 'theside'sof theprimary 'ridges24b and cutting out the secondary ridges '24d rin the same operation.

1From the foregoing, it will be observed'that'assuming thatthe 'blankisv runthrough 'the 'cutters fromV theA exhaust end Bthereof (Fig. 13)that'iirst'the `cutters v36 cut away portions oftheridges 33,' makingthe sides'thereof parallel, a's'indicated'in'Fig. '4, to y'linish theprimary ridges 23I ,'24b. When'the cutters36 Varrive at'the point'C(Fig.

3) they cutaway "the-.notches or Yslots '26, more 'clearly shown in Fig.I6 ofjthedrawings. Thusby one l'sweep of thev arc-chute side-wall blank.35 through vthe gang of cutters, "the finishedisideLwall m'enlberlZla,24 is formed.

Fromthe foregoing it .will be apparent'that wei have described `an'interrupter assembly particularly adapted formagnetic air-type circuitbreakers, the chief advantage off-which is l'simplified manufacture.l'Interrupters of this type at persent are made from flat ceramicplates. For example,.for a rating of 4.l.6/4.76 kv. and 250,000 .kva.,'21%6 inches by l2 inches 'by 3/16 inch thick, 3`2 plates beingruse'dfor each single pole'assembly. These plates are made With'an offsetV-shapednotch extending inwardly for 7 inches from one of the narrowends. Reference may be had to U. S. Patent'2,442,`l`9`9 issued'MayZS,1948, to Robert C. Dickinson and'Russell E. Frink and assigned to theassignee of the-instant application. The plates `are stacked withcemented asbestosrope spacers between the long edges, and with theo'ifset of the notches placed alternately to the right and left of thecenter-line. YSpacersgof accurate thickness are placed between theplates, and the assembly is clamped together and baked so as to set upthe cement. The spacers are then removed. In order to preserve the shapeofthe plates during firing, the plates are pressed with atie across theopen end of the notch. After ring, the 'ties must'be cnt oi.

The structure-of our invention has several advantages over interruptersmade previously by methodsvsomewhat similar `to this. In the previousconstructions, so far as we are aawre, the secondary ridges 24d, 23d hadnot been used, the primary ridges `23,17, '24b projecting in a smoothcurve close to the opposite side-wall member but not meeting it. In this.type of a structure, the arc can go completely through the'interrupterand continueto burn over the other end. .In order to prevent this,anexpensive mutlier must be provided. This muler generates backpressureand impedes theprogress ofthe arc; the theory' being that if the arcmoves slowly enough, interruption will occur before the arc has gonecompletely through the interrupter. On the otherhand, inthe structureaccording'to .our invention, 'the `arc 25 Vwill vbe driven up into thenotches 29 formed between 'the outer edges of the primaryridges 23h, 24hand the sides of the secondary ridges 23d,'2`4d, but will not go beyondthe point A of Figs. 2 and 3, since arc travel beyond thispoint A wouldrepresenta large and abrupt increase in arc energy. This permits 'making'the vexhaust passages V30 (Fig. 6) through the interrupter much freer,bringing magnetic deionization into play. yThe theory of magneticdionization Ahas been thoroughly covered in Ludwig Patent No. 2,243,038,and brieiiy consists of magnetically driving ions yout ofthe arc 25.This'force is transmitted to 'the gas surrounding the arc incollisionsbetween the ions "and the neutral gas molecules. Thus,themoving ions cause un-ionizedgas to`be'plac'ed in 'motionsothat:sr-new supplydf 'melun-ionized gasis constantly 4being drawn past thearc. If the structure is open through, as

in previous designs, in 'which -primary ridges come close to, but neverreach, the opposite wall member, the arc moves along with the air blastand advantage cannot be taken of this method of deionization.

In another type of construction, as set out in Patent No. 2,417,683, thesecondary lridges employed in our invention are not `used and the curve`of the fprimary ridges extends overcompletely to the opposite side-wallmember. Vihile this construction is somewhat superior to the openconstruction, inr'espect to keepinglre'arc insidethe interrupter, thereAis a crack along thegjoint between the primary ridges andthe oppositeside wall member, 'which 'thezarc will erode `out andLmakeiitfv-'eventually like the open structure.

In the latter construction, thearc comes into contact with ceramicsurfaces and heats them to a very high tempcrature so that they tend tobecome conducting. vIn our construction, Ait will 'be observed that 'byeach "joint where the directionof'the 'arc 25 is reversed, as 'shovvnrnFig'. 6, there is a surface bounding the notches'26whir'h does not'comein direct vContact with the farc '2"3. `-'I`hese surfaces will'therefore remain much vcooler and'will retain their V'dielectric`-strength. If the secendaryfridges 23d, 24d are not used,the arcw'illbe again'st'a 'continuous ceramic surface lthroughout its length, -whichwill "be uniformly heated; and `the dielectric strength will vbe muchlower than where these relatively cooler surfaces, forming the 'notches26(Fig. 6'), are'interpos'ed.

'We have kalso disclosed a 'method for manufacture-'ot' the device,whichrcon'sistsoftwo'identical pieces. 'The blank '35 is 'dry-pressed asshown'in "Fig. v7,'zn`1izlafter itis cured, itism'achined `with `gang ofcircuiteeutters 36, vwhich removes'material from'between each of theunfinished primary ridges 33. The milling might belone before or afterfiring thepiece 35. lWhile thestrueture, as described, may be made of'a'red ceramicp'orcelain, it could bemade from any suitable material'for "interf rupters of this type, such as"cold-moldedasbestosiPortland-'cement mixtures, etc.

Although we have'shownan'd described a 'specicstructure, and amethod'o'r process Afor'fo'rmiing the same, it is to be clearlyunderstood that the same 'weremerely for -the purpose "of illustration,and 'that change'sand modifications may readily vbe 'made by those"skilled 'in the art, without departingfrom 'thespirit'and scope'of theinvention.

We claim as our invention:

l. A'circuit-interruptor including relatively movable contacts betweenwhich'a'n arcmaybe'formed'uponopening the circuit, an insulating arc4chute in which thejarc is moved including'spaced side wallmembersfe'ahiside wallmember having onitsside facing the other'sidewallmember -a plurality of primary vridges extending 'lon'gif tudinally inlthe general direction'fof movement r of *said arc throughsaid chute,vatleast some of the primary ridges having'oiset portions to engage theopposite WalL'and a plurality of cooperating secondaryridgcs "in-theIsame general 'plane as the said some primary ridges extending inwardlyfrom the opposite side wall member.

2. A circuit interrupter including relatively movable contacts betweenwhich an arc may be formed upon opening the circuit, an insulating arcchute irl-which'the larc is moved including spaced side Wall members,leachside wall memberhaving onits side Afacing-the other sidewall member`a plurality lof primary ridges extending longiltudinally in the generaldirection of Vmovement'of'said arc Vthrough said chute, at least some-of the primary ridges having 'onset/portions to :engage `'the'opposite`wll,

'a plurality of cooperating relativclyshortsecondary ridges in thesamegeneral plane as the saidsome primary 'ridges extending-inwardly 'fromthe opposite side Wallmenibe'r, 'and lthe offset 'portions extendingoverfand v1engaging-the secondary ridges to form a generally slottedLplate A'construction f f 3. A circuit interrupter including relativelymovable contacts between which an arc may be formed upon opening thecircuit, an insulating arc chute in which the arc is moved includingspaced side wall members, each side wall member having on its sidefacing the other side wall member a plurality of primary ridgesextending longitudinally in the general direction of movement of saidarc through said chute, at least some of the primary ridges havingolfset portions beginning at a point intermediate the ends of the arcchute to engage the opposite wall, a plurality of cooperating relativelyshort secondary ridges in the same general plane as the said someprimary ridges extending inwardly from the opposite side wall member,and the offset portions extending over and engaging the secondary ridgesto form a generally slotted plate construction.

4. A circuit interrupter including relatively movable contacts betweenwhich an arc may be formed upon opening the circuit, an insulating arcchute in which the arc is moved including spaced side wall members, eachside wall member having on its side facing the other side wall mem` bera plurality of primary ridges extending longitudinally in the generaldirection of movement of said are through said chute, the primary ridgesof one side wall member at least partially overlapping the primaryridges of the other side wall member, at least some of the primaryridges having offset portions to engage the opposite wall, and aplurality of cooperating secondary ridges in the same general plane asthe said some primary ridges extending inwardly from the opposite sideWall member.

5. A circuit interrupter including relatively movable contacts betweenwhich an arc may be formed upon opening the circuit, an insulating arcchute in which the arc is moved including spaced side wall members, eachside Wall member having on its side facing the other side wall member aplurality of primary ridges extending longitudinally in the generaldirection of movement of said arc through said chute, the primary ridgesof one side wall member being staggered with respect to the primaryridges of the opposite wall member, at least some of the primary ridgeshaving oiset portions to engage the opposite wall, and a plurality ofcooperating secondary ridges extending inwardly from the opposite sidewall member and being in the same general plane as the said some primaryridges.

6. A circuit interrupter including relatively movable contacts betweenwhich an arc may be formed upon opening the circuit, an insulating arcchute in which the arc is moved including spaced side wall members, eachside wall member having on its side facing the other side wall member aplurality of primary ridges extending longitudinally in the generaldirection of movement of said arc through said chute, the primary ridgesof one wall being slightly spaced from, overlapping and staggered withrespect to the primary ridges of the opposite wall so that the arc inpassing through said chute is forced to take a tortuous closely confinedpath around the outer edges of portions of said primary ridges, at leastsome of the primary ridges having offset portions to engage the oppositewall, and a plurality of cooperating secondary ridges in the samegeneral plane as the said some primary ridges extending inwardly fromthe opposite side wall member.

7. A circuit interrupter of the type wherein an arc is moved within anarc chute formed by the interleaving cooperation of a pair of spacedinsulating side wall members each having a plurality of primary ridgesextending inwardly therefrom, characterized by the fact that at leastsome of the primary ridges have olset portions and that between some ofthe primary ridges are secondary ridges of shorter length in thedirection of arc travel, the secondary ridges being in substantially thesame plane and mating with some of the primary ridges of the oppositewall member to form closed slot portions.

8. The method of making a side-wall member for an arc chute includingthe steps of: forming a blank of insulating material having a pluralityof primary ridges with aligned deep and shallow valleys therebetween,running a pair of spaced cutters along the deep valley, and cutting intothe two bottom corners of the shallow valley to form a second ridge ofless height.

References Cited in the tile of this patent UNITED STATES PATENTS2,306,204 Boehne Dec. 22, 1942 2,393,164 Hobson Jan. l5, 1946 2,417,683Harlow Mar. 18, 1947

